The present invention relates to a gateway apparatus arranged between circuit switched networks and the Internet to repeat data transmitted/received between the circuit switched networks through the Internet.
In recent years, with the development of network technology (increase in bandwidth of a local area network (LAN)), an increase in number of functions of a personal computer (PC), and the development of PC technology (e.g., increase in speed of a CPU (Central Processing Unit)), high-speed communication of sound (audio) data between PCs in a LAN is practically used.
As one of communication technology of sound data, a technology for transmitting the sound data through the Internet constituted by LANs and wide area networks (WANS) is known. This technique is called a voice over IP (VoIP) connection. Application software or systems based on the VoIP connection are called internet telephony (IT) and rapidly put on the market.
In recent years, an internet telephony gateway apparatus (to be referred to as a xe2x80x9cgateway apparatusxe2x80x9d hereinafter), having a gateway function for performing protocol conversion between a circuit switched network such as a telephone network and the Internet, for realizing two-way communication between the circuit switched networks and the Internet is developed. By using the gateway apparatus, an internet telephony system (IT system) for repeating data between conventional circuit switched networks (telephone networks) through the Internet is realized. The communication charge of this IT system is cheaper than the communication charge of a conventional system using the telephone network. Therefore, the IT system and services based on the IT system rapidly spread.
In the IT system described above, when sound data is transmitted/received between circuit switched networks through the Internet, an sound communication channel corresponding to a call between the circuit switched networks (between terminal devices) is set between gateway apparatuses on the Internet. In this manner, a call is set between the circuit switched networks (between the terminal devices). Thereafter, sound data is transmitted by using the installed communication channel. The sound communication channel is set such that the gateway apparatuses on an call-out side and an call-in side execute a procedure (to be referred to as a xe2x80x9cH.323 procedurexe2x80x9d hereinafter) based on H.323 protocol to the call set between the circuit switched networks. H.323 protocol is a communication protocol corresponding to VoIP recommended by ITU-T.
FIG. 13 is a sequence chart showing H.323 procedure. As shown in FIG. 13, H.323 procedure is constituted by the following procedures:
(1) A connection procedure (see procedure A in FIG. 11) of a control channel (to be referred to as a xe2x80x9cQ.931 channelxe2x80x9d hereinafter) based on Q.931 protocol;
(2) A connection procedure (see procedure B in FIG. 13) of a control channel (to be referred to as a xe2x80x9cH.245 channelxe2x80x9d hereinafter) based on H.245 protocol; and
(3) A connection procedure (see procedure C in FIG. 13) of an sound channel.
As described above, the sound communication channel is constituted by the Q.931 channel, the H.254 channel, and the sound channel. These three channels are connected and established by the procedures A to C to establish a call. Thereafter, transmission and reception of sound data between the circuit switched networks are started.
In this case, Q.931 protocol is a communication protocol based on the basic call control specification of ISDN user network interface layer 3, and the Q.931 channel is a basic call control channel on the Internet. H.245 protocol is control protocol for multimedia communication, and the H.245 channel is a control channel for multimedia communication. The protocol and the channel are used to exchange capability data between the gateway apparatuses. The sound channel is a channel for transmitting an IP packet in which sound data is stored.
Conventionally, the H.323 procedure is started when the gateway apparatus on the call-out side receives call setting request between circuit switched networks from the circuit switched network on the call-out side. For this reason, the H.323 procedure must be executed from time when the circuit switched network transmits a call setting request to time when the circuit switched networks on the call-out side and a call-in side starts transmission/reception of sound data.
When the gateway apparatus on the call-out side receives a plurality of call setting requests from the circuit switched network on the call-out side, the H.323 procedures corresponding to the call setting requests are executed in the reception order. For this reason, when the gateway apparatus on the incoming side receives a large number of call setting requests for a short time (when a traffic intensity increases) execution of H.323 procedures corresponding to call setting requests, which are relatively lately received, of the large number of call setting requests is delayed, and a call setting (connection) process between the circuit switched networks and the start of transmission/reception of sound data may be delayed.
It is an object of the present invention to provide a gateway apparatus being capable of suppressing the probability that a call connection process (call setting process) is delayed even if a traffic intensity between low-order networks in a complex network in which a plurality of low-order networks (e.g., circuit switched networks) are connected to a high-order network (e.g., the Internet) through the gateway apparatus.
The present invention employs the following configuration to solve the problem described above.
The first aspect of the present invention, there is provided a gateway apparatus arranged between a circuit switched network and the Internet comprising: a prior connection section setting a channel on the Internet according to a call setting request received from the circuit switched network before the call setting request is received from the circuit switched network; and a call setting section setting a connection corresponding to the call setting request on the Internet by using the communication circuit set by the prior connection section when the call setting request is received from the circuit switched network.
According to the first aspect, since the communication circuit is set by the prior connection section in advance, the process of setting the channel need not be performed when a connection corresponding to the call setting request is set by the call setting section. Therefore, since time required for the call setting process (call connection process) can be shortened, the probability that the call setting process is delayed when a traffic intensity increases can be suppressed.
In the present invention, the Internet indicates network using the internet protocol (IP) as protocol of layer 3, i.e., indicates an internet protocol network, and includes intranets and the like. In addition, the circuit switched network is, for example, a telephone network or a PBX network.
In the second aspect of the present invention, there is provided a gateway apparatus, arranged between a circuit switched network and the Internet, executing a connection procedure of a control channel based on Q.931 protocol, a connection procedure of a control channel based on H.245 protocol and a connection procedure of an sound channel according to a call setting request received from a circuit switched network, comprising: a prior connection section executing the connection procedure of the control channel based on Q.931 protocol before the call setting request is received from the circuit switched network; and a call setting section setting a connection corresponding to the call setting request on the Internet by using the control channel based on Q.931 protocol set by the prior connection section when the call setting request is received from the circuit switched network
According to the second aspect, since the control channel based on Q.931 protocol is set by the prior connection section in advance, when the call setting section sets a call corresponding to the call setting request, the connection procedure of the control channel based on Q.931 protocol need not be performed. Therefore, since time required for the call setting process (call connection process) can be shortened, the probability that the call setting process is delayed when a traffic intensity increases can be suppressed.
The third aspect of the present invention is specified as follows. That is, the connection procedure of a control channel based on H.245 protocol is executed before the prior connection section according to the second aspect receives a call setting request received from the circuit switched network, and when the call setting request is received from the circuit switched network the call setting section sets a call corresponding to the call setting request by using the control channel based on Q.931 protocol and the control channel based on H.245 protocol set by the prior connection section. With this configuration, time required for the call setting process can be made shorter than that in a case wherein the connection procedure of the control channel based on H.245 protocol after the call setting request is received.
The fourth aspect of the present invention is specified as follows. That is, the prior connection section according to the third aspect executes the connection procedure of the sound channel before the call setting request is received from the circuit switched network, and when the call setting request is received from the circuit switched network, the call setting section sets the connection corresponding to the call setting request on the Internet by using the control channel based on Q.931 protocol, the control channel based on H.245 protocol, and the sound channel set by the prior connection section. With this configuration, time required for the call setting process can be made shorter than that in a case wherein the connection procedure of the sound channel after the call setting request is received.
The fifth aspect of the present invention is specified as follows. That is, the gateway apparatus according to the second aspect further comprises: a traffic monitor section monitoring a traffic volume in the gateway apparatus; and a channel count change section changing the number of control channels based on Q.931 protocol connected by the prior connection section according to a monitor result of the traffic monitor section.
The sixth aspect of the present invention is specified as follows. The gateway apparatus according to the third aspect further comprises: a traffic monitor section monitoring a traffic volume in the gateway apparatus; and a channel count change section changing the number of control channels connected by the prior connection section and based on Q.931 protocol and the number of control channels connected by the prior connection section and based on H.245 protocol depending on a monitor result of the traffic monitor section.
The seventh aspect of the present invention is specified as follows. The gateway apparatus according to the fourth aspect further comprises: a traffic monitor section monitoring a traffic volume in the gateway apparatus; and a channel count change section changing the number of control channels connected by the prior connection section and based on Q.931 protocol, the number of control channels connected by the prior connection section and based on H.245 protocol, and the number of sound channels connected by the prior connection section depending on a monitor result of the traffic monitor section.
The channel count change sections according to the fifth to seventh aspects increase the numbers of control channels when traffic intensities increase and decrease the numbers of control channels when traffic intensities decrease.
According to the fifth to seventh aspects, since the numbers of control channels can be changed depending on the traffic intensities, call setting processes in the gateway apparatuses can be efficiently operated, and resources related to the connection of the control channels can be efficiently used.
The eighth aspect of the present invention is specified as follows. The gateway apparatus according to the second aspect further comprises: a channel count change section changing the number of control channels connected by the prior connection section and based on Q.931 protocol depending on an input channel count change request.
The ninth aspect of the present invention is specified as follows. The gateway apparatus according to the third aspect further comprises: a channel count change section changing the number of control channels connected by the prior connection section and based on Q.931 protocol and the number of control channels connected by the prior connection section and based on H.245 protocol depending on an input channel count change request.
The tenth aspect of the present invention is specified as follows. The gateway apparatus according to the fourth aspect further comprises: a channel count change section changing the number of control channels connected by the prior connection section and based on Q.931 protocol, the number of control channels connected by the prior connection section and based on H.245 protocol, and the number of sound channels connected by the prior connection section depending on an input channel count change request.
According to the eighth to tenth aspects, as in the fifth to seventh aspects, call setting processes in the gateway apparatus can be efficiently operated, and resources related to the connection of the control channels can be efficiently used.
The eleventh aspect of the present invention is specified as follows. That is, the gateway apparatuses according to the eighth aspect further comprises input devices for inputting channel count change requests.
The twelfth aspect of the present invention is specified as follows. That is, the channel count change requests in the eighth aspect is input from the circuit switched networks.
In the eighth aspect, the channel count change request may be input from terminal devices directly connected to the gateway apparatuses or input from terminal devices connected to the gateway apparatuses through circuit switched networks.